Python Program to Check if Number is Armstrong

Python Program to Check if Number is Armstrong

An n-digit number abcd.. is said to be an Armstrong number if it obeys the following condition:

abcd.. = pow(a,n) + pow(b,n) + pow(c,n) + ...

For example:

153 = pow(1,3) + pow(5,3) + pow(3,3) = 1 + 125 + 27 = 153

In this tutorial, we will write a Python function to check if a given number is an Armstrong number and explore various examples.

Python Armstrong Function

The following function armstrong() takes a number as an argument and checks if the number is Armstrong or not. The function returns True if the given number is Armstrong, or False otherwise.

def armstrong(num):
    num = str(num)
    n = len(num)
    result = 0
    # Compute sum of powers
    for i in num:
        result += pow(int(i), n)
        # Early exit if result exceeds the number
        if result > int(num):
            break
    # Check if the number equals the sum of powers
    return int(num) == result

Explanation:

  1. The function converts the number to a string to iterate over its digits.
  2. The length of the number (n) is calculated using len(num).
  3. A for loop calculates the sum of each digit raised to the power of n.
  4. The if result > int(num) condition optimizes the function by exiting early if the computed result exceeds the original number.
  5. The function checks if the sum equals the original number and returns True if they match; otherwise, it returns False.

Example 1: Check if a Given Number is Armstrong

In this example, we read a number from the user and check if it is an Armstrong number.

Python Program

def armstrong(num):
    num = str(num)
    n = len(num)
    result = 0
    for i in num:
        result += pow(int(i), n)
        if result > int(num):
            break
    return int(num) == result

# Read the number from the user
num = input("Enter a number: ")
result = armstrong(num)
print(f"Is {num} an Armstrong Number? {result}")

Explanation:

  1. The user enters a number as input, which is passed to the armstrong() function.
  2. The function computes if the number is Armstrong and returns a boolean result.
  3. The program displays the result to the user.

Output:

Enter a number: 153
Is 153 an Armstrong Number? True

Example 2: Check Armstrong Numbers for Multiple Inputs

This example demonstrates checking Armstrong numbers for a list of inputs.

Python Program

def armstrong(num):
    num = str(num)
    n = len(num)
    result = 0
    for i in num:
        result += pow(int(i), n)
        if result > int(num):
            break
    return int(num) == result

# List of numbers to check
numbers = [153, 9474, 9475, 370]
for num in numbers:
    print(f"Is {num} an Armstrong Number? {armstrong(num)}")

Explanation:

  1. A list of numbers is defined for checking.
  2. The program iterates through each number in the list and checks if it is an Armstrong number using the armstrong() function.
  3. Results are printed for each number.

Output:

Is 153 an Armstrong Number? True
Is 9474 an Armstrong Number? True
Is 9475 an Armstrong Number? False
Is 370 an Armstrong Number? True

Example 3: Armstrong Numbers in a Range

This example finds all Armstrong numbers within a specified range.

Python Program

def armstrong(num):
    num = str(num)
    n = len(num)
    result = 0
    for i in num:
        result += pow(int(i), n)
        if result > int(num):
            break
    return int(num) == result

# Find Armstrong numbers in a range
start, end = 100, 10000
print(f"Armstrong numbers between {start} and {end}:")
for num in range(start, end):
    if armstrong(num):
        print(num, end=" ")

Explanation:

  1. The range of numbers is specified using start and end.
  2. The program iterates through the range and checks each number using the armstrong() function.
  3. Armstrong numbers are printed in a single line, separated by spaces.

Output:

Armstrong numbers between 100 and 10000:
153 370 371 407 1634 8208 9474

Summary

In this tutorial, we explored how to check if a number is an Armstrong number using Python. We covered:

  • Writing a function to check for Armstrong numbers.
  • Examples for single and multiple inputs.
  • Finding Armstrong numbers within a specified range.

Each method provides insights into solving related problems, emphasizing flexibility and efficiency.

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